By-pass of an electrical component

ABSTRACT

A modular by-pass device of an electrical component includes a housing possessing a movable means of sealing, and is equipped with conducting terminals, one of whose ends is connected to one of the terminals of the electrical component circuit, the other end being fastened to the wall of the housing projecting into the interior of the housing and constituting a contact post. An actuator providing transposition between two positions of a control device include a plunger shaft and a spring arranged in the space formed between the plunger shaft and the internal wall of the housing. A trigger includes a retention device of the plunger shaft held in place by a fusible material. A reversing switch includes a contact zone providing electrical continuity between two contact posts of the terminals carried by the housing. The disclosed embodiments finds application more particularly in the isolation and short-circuiting of a battery element, which has become defective.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the National Stage of International Application No.PCT/EP2006/011063 International Filing Date, 17 Nov. 2006, whichdesignated the United States of America, and which InternationalApplication was published under PCT Article 21 (2) as WO Publication No.WO2007/140810 and which claims priority from French Application No.0605033 and 060532 both filed on 7 Jun. 2006, the disclosures of whichare incorporated herein by reference in their entireties.

BACKGROUND

1. Field

The disclosed embodiments concern a by-pass device of an electricalcomponent, such as a module by-pass device, and more particularly athermally activated by-pass device using a control current. It findsapplication more particularly in the isolation and short-circuiting of abattery element, which has become defective.

2. Brief Description of Related Developments

Protection against defective batteries has been the subject of numerousstudies, in particular of difficult to access batteries, such as thoseon board space missiles.

In fact, when a battery element becomes defective, it is imperative toisolate it so that it shall not impair the functioning of sound batteryelements, which may continue to work and to supply potential to thecircuit, which the battery has to supply.

Generally speaking, by-pass devices also called battery by-passes,consist of an actuator, a trigger and a reversing switch located in ahousing, each of these three components possessing its own function.Thus, the actuator is a mechanical device, which has to be able toprovide the transposition between two positions of a control devicecalled a shaft or a plunger. The trigger is a mechanical devicecomprising a fusible material, which when subjected to an electriccontrol current producing a rise in temperature will melt or break inorder to set free the actuator. The reversing switch is a device, whichprovides in each of its two positions electrical continuity between twoof the three terminals carried by the housing and connected to thebattery element circuit terminals.

At one of its ends, the shaft generally speaking comprises a flange,which serves as a stop to a spring located in the space provided betweenthe shaft and the internal wall of the housing. This space comprises acircular shoulder cut the internal surface of the housing in such a wayas to trap the spring between the shaft collar and the circularshoulder. The spring is thus kept in compression, whilst the shaft isheld in sheathed position by the trigger, that is to say, when the shaftholds the reversing switch in its normal position of functioning andwhen electrical continuity between the two first terminals is provided.In the event of the dysfunction of a battery element, the trigger isactuated and thereby sets free the shaft. The latter is then transposedfrom its sheathed position to the freed position under the pressure ofthe spring. This position freed by the trigger makes it possible for theshaft to bring the reversing switch into a position of isolation of thefailed battery element by providing electrical continuity between afirst and a second terminal.

Triggers which use a fusible material, which melts or breaks on a risein temperature of the material by the passage of an electric current,are well known.

This principle is described in U.S. Pat. No. 3,388,933, which deals witha trigger comprising a fusible element, which keeps half-shells able tobe separated for the purpose of the maintenance and the setting free ofa voluminous object fixing hoop.

An application of this principle is, in particular, disclosed by U.S.Pat. No. 3,924,688, which describes the setting free of an actuatorshaft kept in contact by two locked half-shells by means of a wire coilunder strain, whose slackening is controlled by the melting of a fusibleelement. The slackening of the coil makes possible the separation of thetwo half-shells and hence the setting free of the shaft.

An improvement to this principle is disclosed in U.S. Pat. No.5,471,888, which describes an embodiment comprising two half-shells andan insulator on which the fusible element is placed.

The technology of actuators making possible the separation of an elementof a battery when the latter exhibits an anomaly, by a physicalseparation of the two parts of an assembly, thanks to the melting of anelement reacting to an electrical threshold, is likewise well known.

U.S. Pat. No. 5,362,576 concerns a conducting plunger placed between twoterminals constituting the ends of an insulating cylinder. An outputterminal is connected to the battery element. When it is functioningnormally, the plunger is kept in electrical contact with the terminalthrough a fusible element. The current then passes between the terminalsthrough the plunger, which also comprises peripheral contacts in theform of metal sleeves. When an electric threshold is exceeded,corresponding to an increase of the internal resistance of the batteryelement, the thermal element weakens, melts and breaks. The plunger isthen propelled through the relaxing of the strain of the spring andafter having broken the electrical continuity between the firstterminals, provides a by-pass connection by connecting the first andsecond terminal.

U.S. Pat. No. 5,438,173 deals with a battery by-pass device comprising amobile mounting consisting of a base, a compression spring, an elementcomprising erasable arms, which hold in place a plunger. The saidplunger is equipped with a freeing means which comes into play in thecase of a failure via the erasure of the arms, thus setting free themobile mounting and making it possible to establish an electricalby-pass circuit.

U.S. Pat. No. 6,249,063 discloses a conducting half-shaft, carryingtoroidal contacts, mechanically connected to an insulating half-shaftproviding electrical continuity between the terminals, the plungerconnected mechanically to the insulating half-shaft being held by twohalf-shells, themselves held in contact by a wire coil under strain, thesaid strain being released when a fusible element on its electricalthreshold is destroyed. More particularly this document describes amodular by-pass device of an electrical component comprising a housingpossessing a movable means of sealing and equipped with conductingterminals, one of whose ends is connected to one of the terminals of theelectrical component circuit, the other end being fastened to the wallof the housing projecting into the interior of the housing andconstituting a contact post, an actuator providing transposition betweentwo positions of a control device consisting of a plunger shaft andcomprising a spring arranged in the space formed between the plungershaft and the internal wall of the housing, a trigger comprising aretention device of the plunger shaft held in place by a fusiblematerial, a reversing switch comprising a contact zone providingelectrical continuity between two contact posts of the terminals carriedby the housing.

All the embodiments described in the prior art use a relatively largenumber of parts, which may become separated when used in demandingenvironments, which are costly to assemble and which cannot be used inall models required by customers. Moreover, the said large number ofparts does not make possible easy on-site assembly, maintenance orrepair of the devices.

There is accordingly a need to provide a modular by-pass device of anelectrical component offering a high degree of flexibility in use, forthe adaptation, the introduction and the replacement of differentcomponents.

Such a device must be modular and must moreover make possible absolutesafety, in order to avoid during the assembly and fitting in workshops,any danger of untimely triggering. Lastly, in the event of

untimely triggering, the device must make possible the repositioning ofcomponents without complete dismantling.

SUMMARY

The aspect of the disclosed embodiments is that of making possible easyadaptation, fitting, fastening and replacement of different types oftrigger as well as different types of reversing switches at the end inquestion of plunger shafts.

This is the reason why the disclosed embodiments concern a modularby-pass device of an electrical component comprising a housingpossessing movable means of sealing and equipped with conductingterminals, one of whose ends is connected to one of the electricalcomponent circuit terminals, the other end being fastened on the housingwall, projecting the interior of the housing and constituting a contactpost, an actuator able to provide transposition between two positions ofa control device consisting of a plunger shaft and comprising a springarranged in the space formed between the plunger shaft and the internalwall of the housing, a trigger comprising a retention device of theplunger shaft held in place by a fusible material, a reversing switchcomprising a zone of contact providing electrical continuity between twocontact posts of terminals carried by the housing, a by-pass device inwhich the plunger shaft of the actuator is a one-piece shaft.

According to the disclosed embodiments, the plunger shaft comprises atone of its ends a cylindrical portion in the form of a barrel providedwith a central bore forming a seating.

According to the disclosed embodiments, the trigger comprises an adapterheld in place by friction within the bore of the central seating.

According to a variant of the disclosed embodiments, the open end of theseating is provided with a thread on its interior surface.

According to the said variant, the trigger comprises an adapter held inplace by screwing the plunger shaft into the thread of the seating.

According to a first embodiment, the adapter comprises a thread, whichreceives a screw forming a torque kept in a locked position by at leastone tappet acting in concert with at least one turn of the screw fittedin a coil and kept in locked position by a retaining wire hooked onto afusible element.

According to a second embodiment, the adapter comprises a post carryingan ogival pin supported on at least one tappet fitted in a coil and keptin locked position by a retaining wire hooked on a fusible element.

Using these two methods, when the fusible element melts, the tappetsseparate by a lateral sliding movement.

According to a third embodiment, at least one tappet comprises an armwhose edge supports itself in a groove of the end portion of thetrigger. Using this method, when the fusible element melts, the tappetseparates by a pivoting movement.

The disclosed embodiments also concern a modular by-pass device of anelectrical component comprising a housing possessing a movable means ofsealing and equipped with conducting terminals, one of whose ends isconnected to one of the electrical component circuit terminals, theother end being fastened to the housing wall and projecting into theinterior of the housing and constituting a contact post, an actuatorproviding the transposition between two positions of a control deviceconsisting of a plunger shaft and comprising a spring arranged in thespace formed between the plunger shaft and the interior wall of thehousing, a trigger comprising a plunger shaft retention device held inplace by a fusible element, a reversing switch comprising a contact zoneproviding electrical continuity between two contact posts of terminalscarried by the housing, a by-pass device in which the plunger shaft ofthe actuator is a one-piece shaft.

According to the disclosed embodiments, the plunger shaft comprises atone of its ends a cylindrical portion in the shape of a pin providedwith a threaded portion.

According to a preferred embodiment, the plunger shaft is made of aconducting material and according to a variant, the plunger shaft ismade of an insulating material.

According to a preferred embodiment, the reversing switch is equippedwith a jacket, which, if it is conducting, provides electricalcontinuity between the posts according to the position of the plungershaft.

According to this embodiment, an insulating strut and an insulating shimprovide the positioning and the locking of the conducting jacket.

According to a first embodiment, the contact posts are equipped with acircular metal contacts strip projecting into the housing space.

According to a second embodiment, the conducting jacket comprisesrecesses for positioning the circular metal contacts strip projectinginto the housing space.

According to a third embodiment, the jacket has the form of a keyreception seating made of a conducting material providing electricalcontinuity between the posts according to the position of the plungershaft.

According to this embodiment, the keys are kept in place using a snapring and kept in compression using springs placed in the seating andacting on the keys. In a variant, the spring is an individual one,either attached or incorporated.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed embodiments shall be better understood with the help ofthe following description and drawings, which are appended thereto andin which

FIG. 1 is a section of an embodiment of the by-pass;

FIGS. 2 a and 2 b are a section of a trigger element according to afirst embodiment;

FIGS. 3 a and 3 b are a section of a trigger element according to asecond embodiment;

FIG. 4 is a section of a trigger element according to a thirdembodiment;

FIG. 5 is a section of a reversing switch element according to a firstembodiment;

FIG. 6 is a section of a reversing switch element according to a secondembodiment;

FIGS. 7 a and 7 b are a section of a reversing switch element accordingto a third embodiment.

DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS

The by-pass device, by-pass 1 comprises a cylindrical housing 2 madefrom an insulating material provided at its ends with movable means ofsealing 3 and 4, fastened to a cylindrical wall with the help of dowels5. Terminals T1 and T3 pass through the wall of housing 2 and it shouldbe noted that T2 is not shown in FIG. 1. These terminals, which providethe supply for T1 and T2 and the by-pass function for terminals T2 andT3, are connected by their end located outside the housing to thecircuit terminals of the battery element, which is not shown. Theannular end of each of the terminals T1, T2 and T3 located insidehousing 2 provides a contact post P1, P2 and P3, whose role is describedbelow.

Housing 2 comprises on its interior surface 6, two shoulders 7 and 8,which correspond to the change of diameter between internal sections D1and D2 of housing 2.

Housing 2 is provided for receiving the three elements constituting theby-pass, namely, an actuator 9, a trigger 10 and a reversing switch 11,which make it possible to isolate with the help of a control current, abattery element which has become defective and so ensure the correctfunctioning of the remaining cells of the battery.

Each of these three elements possesses its own function.

Actuator 9 is a mechanical device, which provides a transpositionbetween two positions of a control device called plunger shaft 12.Trigger 10 is a device comprising retention means and having a fusiblematerial, which, when it is subjected to an electric current producing arise in temperature, melts or breaks in order to set free the actuator9. Reversing switch 11 is a device providing in each of its twopositions an electrical continuity between the three terminals T1, T2and T3 connected to battery element circuit terminals.

According to the embodiment shown in FIG. 1, the by-pass comprises thehousing 2 made of insulating material inside which is positioned andguided the plunger shaft 12, which is electrically conducting and ableto be transposed. Clearly, according to the design of the modelrequested by the customer, the plunger shaft can be made from insulatingmaterial. In both cases, the plunger shaft 12 is a one-piece shaft.

The plunger shaft 12 comprises at its end, which is contiguous with thepart of the housing receiving the actuator 10, a cylindrical portion inthe form of barrel 13, provided with a central bore forming a seating14. The open end of the seating 14 is provided with a collar forming aflange 15 oriented towards the exterior of the seating. The plungershaft 12 comprises at the end contiguous with the part of the housingreceiving the reversing switch 11, a cylindrical part in the form of apin 16. The plunger shaft comprises in it central part a shoulder 17formed by the difference of the respective diameters of the cylindricalparts of the pin 16 and the barrel 13, the said shoulder constituting anend-of-travel stop of the means of positioning and locking of the partsof the reversing switch 11. The pin 16 is also provided on its exteriorsurface with a thread 18, which makes possible the easy replacement andfastening of reversing switch parts.

The open end of seating 14 makes possible the easy replacement andfastening of parts, which equip the trigger 10 thanks to its centralbore. Generally speaking, these parts consist of an adapter 20 such as aplug made from insulating or other material, which supports the flange15 of the seating and which through friction provides the holding inplace of parts of the trigger in the interior of the seating. In avariant, the seating comprises a thread 19, which makes possible thereplacement and fastening of parts thanks to a bolt, which is able toscrew the adapter fully into the thread 19.

To provide the transposition of the plunger shaft 12 between a sheathedposition, that is to say when the plunger shaft is kept functioningnormally by the trigger 10 and when the posts P1 and P2 are connected, aspring 21 is arranged coaxially on the external surface of thecylindrical portion of the barrel 13. The said spring 21 is kept incompression in the space D2 formed between the exterior surface of theshaft and the internal wall 6 of the housing, between the flange 15 ofthe barrel of the plunger shaft and the circular shoulder 8 made on theinternal surface of the housing. When trigger 10 comes into play, thatis to say, during the abnormal functioning of a battery element, theslackening of the spring 21 moves the plunger shaft into the space D1where parts of the trigger are positioned and the posts P2 and P3 arethen connected.

FIGS. 2 a and 2 b show a first embodiment of the trigger 10, in whichthe bolt is screwed into the thread 19 of the seating 14. The said boltcomprises a collar, which serves as collar 15 and is provided on itscentral axis with a thread 22, supporting a screw 23 and thus generatesa torque. The bolt is locked in rotation in a groove cut into theinternal wall of the housing, into which it slides.

The screw 23 comprises a cylindrical part 24 in which grooves 25 havebeen cut and have a cam section, which can be seen in FIG. 2 b, in whichtappets 26 keep the screw 23 locked in a torque.

The tappets 26 are assembled in a coil 27 and are held in a lockedposition by a retaining wire 28 hooked on one side on the coil and onthe other side on fusible wire or brace 29.

When an electric current exceeding a certain threshold value passesthrough the fusible element 29, the latter melts, sets free theretaining wire 28, which unrolls and makes possible separation of thetappets 26 by a lateral slide movement, thanks to the torque generatedby the screw 23 and the thread 22 of the bolt and to the cam section ofthe supporting surface 25 with the end of the tappets 26.

According to this embodiment, the tappets 26 are two in number and arefitted in an opposing manner. Nevertheless, depending on the size of theapplication, the use of one or more tappets is possible.

In a variant, the link via a bolt may be located in the interior of thecylindrical part 24, the screw then forming part of the plunger shaft,or of an insulating part at the end of the shaft. It should also benoted that in the case of a shaft made of a conducting material, it isnecessary to insulate the trigger/shaft link in order to prevent thepotential of the terminals of the reversing switch from interfering withthe potential of the fusible wire of the trigger.

FIGS. 3 a and 3 b show a second embodiment of the trigger 10, in whichthe adapter 20 nests in the central bore of seating 14. The adapter 20which is made of an insulating material, comprises an insulating collar30, which supports and covers the flange 15 and apart from insulating,guides the plunger shaft 12 during its movement into the space D1. Theadapter 20 comprises opposite its shrunk-on part, a post 31 on which isfastened an ogival or conical metal pin 32. The metal pin rests againstthe tappets 26, which number three in the present embodiment, such ascan be seen in FIG. 3 b. As in the preceding embodiment, the tappets 26are guided into a coil 27 and are held in place by a retaining wire 28hooked on one side on the coil and on the other side to the fusibleelement 29. According to this embodiment, the tappets 26 are three innumber and are fitted in opposition to one another. Nevertheless,depending on the size of the application, the use of a single or severaltappets is possible in conjunction with a bevelled metal pin.

When an electric current exceeding a certain threshold value passesthrough the fusible element 29, the latter melts, sets free theretaining wire 28 which unrolls and makes possible a lateral slidingmovement of the tappets 26 between the flanges of the coil, thanks tothe form of the support between the metal pin 32 and the interiorbevelled part of the tappets 26, the metal pin 32 now moving into thespace D4 formed in the end part of the trigger 10.

FIG. 4 shows a variant of the embodiment shown in FIG. 3. The principleis identical, except for the manner of functioning of the tappets 26. Asin the preceding embodiment, the metal pin supports itself on thetappets 26, but, contrary to the preceding embodiments, the tappets 26are not guided into the coil 27 when they separate. In fact, the tappets26 have an arm 33, which has an edge at its end supporting itself in thegroove 34 cut into the end of the trigger 10. As in the precedingembodiment, the tappets are held in position by a retaining wire 28hooked on one side on the coil and on the other side on a fusibleelement 29. Similarly, according to the present embodiment, the tappets26, which number three, are fitted opposite one another. Nevertheless,depending on the size of the application, the use of a single or severaltappets is possible in conjunction with a bevelled metal pin.

When an electric current in excess of a given threshold passes throughthe fusible element 29, the latter melts, sets free the retaining wire28, which unrolls and makes possible the separation of the tappets 26 bya pivoting movement, as shown by the arrow F, thanks to the form of thesupport between the metal pin 32 and the bevelled interior part of thetappets 26. The metal pin 32 then moves into the space D4 in the endpart of the trigger 10.

FIG. 5 shows a first embodiment of the reversing switch 11. On thesurface of posts P1-P3 seated in the recesses 35 cut into the internalsurface 6 of the housing 2 made of an insulating material, are fastenedcircular metal contact strips 36 of the type manufactured byMulti-Contact AG. These contacts project into space D3 of the housinginto which the pin 16 of the plunger shaft 12 is transposed.

The reversing switch 11 is also equipped with a jacket 37, whosefastening is operated by screwing on the threaded part 18 of the pin 16of the plunger shaft 12. A final positioning and locking strut 38 of thejacket is seated between the first end of the jacket 37 and the bevel 17of the shaft. A shim 39 is located between a second end of the jacket 37and the movable sealing part 3 of the housing.

If the jacket 37 is conducting, the strut 38 as well as the shim 39, aremade of an insulating material, in order to achieve the insulation ofthe conducting jacket 37 from the neighbouring post P1 and the sealingpart 3.

Clearly, the jacket 37 can be fastened by any means other than screwing,for example by using clips, since this operation makes possible itssubsequent replacement.

In normal functioning, that is to say when the plunger shaft is held insheathed position by the trigger, the supply circuit is established byconnecting the jacket 37 and the contacts 36 which equip the posts P1and P2, so providing electrical continuity of the circuit. In the eventof an incident on the battery elements, the trigger 10 sets free theplunger shaft 12 which under the action of the slackening of the spring21 is transposed, enabling the conducting jacket 37 to establish theconnection between the contacts 36 which equip the posts P2 and P3, soproviding the electrical continuity of the by-pass circuit.

FIG. 6 shows a second embodiment in which two circular metal contact 36are each positioned in a recess 40 cut into the outside surface of theconducting jacket 37. As in the preceding embodiment, the contactsproject into the space D3 of the housing into which the pin 16 istransposed. In normal functioning, that is to say, when the plungershaft is held in a sheathed position by the trigger, the supply circuitis established by the connection of the jacket 37 carrying the contacts26 and the posts P1 and P2. In the event of an incident on the batteryelement, the trigger 10 sets free the plunger shaft 12 which istransposed under the action of the slackening of the spring 21, allowingthe jacket 37 to establish the connection between the contacts 36carried by the jacket and the posts P2 and P3, so providing the by-pass.

According to a variant of the embodiment, the width and the spacing ofthe posts P1, P2 and P3 with respect to the conducting jacket 37 are ofa size such as to allow either the isolation or short-circuiting of thethree posts during commutation.

FIGS. 7 a and 7 b show a third embodiment in which the pin 16 receiveson its threaded end part 18 a jacket in the form of a seating 41, whichis locked between the strut 38 surrounding the pin 16 and the shim 39,making it possible to position the keys 42 made of conducting materialarranged concentrically in the seating 41, as shown in FIG. 7 b. Thekeys are held in place with the help of a snap ring 43 and can be keptin compression during functioning with the help of the circular springs44 positioned in the seating 41 and acting on the keys 42. As in thepreceding embodiment, the keys assembly provides electrical continuityby the connection of the posts P1, P2 and P3 depending on the positionof the plunger shaft.

According to a first variant of the present third embodiment, each ofthe key 42 is kept in compression by an individual spring in the seating41.

According to a second variant of the present third embodiment, the keys42 are made of beryllium bronze and provided with an incorporated springarm, which keeps every key equipped in this way in compression with thehelp of an individual spring positioning itself in the seating 41 duringthe fitting of the key.

The disclosed embodiments are not limited to the characteristics of thedevices described but, on the contrary, comprises any device makingpossible the assembly, the disassembly and the replacement of elementsconstituting a modular by-pass device of an electrical component.

The invention claimed is:
 1. A modular by-pass device of an electricalcomponent comprising: a housing comprising: a movable means of sealing;and a plurality of conducting terminals, each having an end connected toan electrical component circuit, and each having another end fastened toa wall of the housing and projecting into an interior of the housing toform a contact post, an actuator providing transposition between twopositions of a control device comprising a plunger shaft and a springarranged in a space formed between the plunger shaft and an internalwall of the housing, a trigger comprising: a retention device of theplunger shaft held in place by a fusible material, and an adapter heldin a central bore of the plunger shaft, and a reversing switchcomprising a contact zone providing electrical continuity between atleast two of the contact posts of the terminals, wherein the plungershaft of the actuator is a one-piece shaft equipped with a shouldercomprising an end with a cylindrical part in the form of a barrelcomprising the central bore and a first seating providing replacementand fastening of the trigger, and wherein the adapter comprises a postcarrying an ogival first pin supported by at least one tappet, the saidat least one tappet fitted in a coil and held in a locked position by aretaining wire hooked on the fusible material.
 2. A modular by-passdevice according to claim 1, wherein the shoulder comprises another endhaving a cylindrical portion in the form of a second in providingreplacement and fastening of the reversing switch.
 3. A modular by-passdevice according to claim 2, wherein the reversing switch comprises ajacket held in place by screwing into a thread of the second pin.
 4. Amodular by-pass device according to claim 3, wherein the jacket isconducting and provides electrical continuity between the at least twocontact posts depending on a position of the plunger shaft.
 5. A modularby-pass device according to claim 4, wherein an insulating strut and aninsulating shim provide positioning and locking of the conductingjacket.
 6. A modular by-pass device according to claim 3, wherein thejacket comprises a second seating for receiving keys made of conductingmaterial.
 7. A modular by-pass device according to claim 6, wherein thekeys are held in place by a snap ring.
 8. A modular by-pass deviceaccording to claim 6 wherein the keys are kept in compression withsprings positioned in the second seating.
 9. A modular by-pass deviceaccording to claim 6, wherein each of the keys is kept in compressionwith individual springs positioned in the second seating.
 10. A modularby-pass device according to claim 6, wherein each of the keys is kept incompression with an integrated individual spring positioned in thesecond seating.
 11. A modular by-pass device according to claim 2,wherein the at least two contact posts are equipped with circular metalcontact strips projecting into the interior of the housing.
 12. Amodular by-pass device according to claim 11, wherein the conductingjacket comprises recesses for positioning the circular metal contactstrips projecting into the interior of the housing.
 13. A modularby-pass device according to claim 1, wherein the adapter is held byscrewing into a thread of the first seating of the plunger shaft.
 14. Amodular by-pass device according to claim 1, wherein the adapter is heldby friction in the central bore of the first seating of the plungershaft.
 15. A modular by-pass device according to claim 1, wherein on themelting of the fusible material, the tappets separate by a lateralsliding movement.